Conventionally, a typical low-magnification photographing lens system which is not specifically designed for macro photography (close-up photography) can be used as a macro lens system by advancing the entire lens system to focus on an object at a short distance to obtain an in-focus paraxial object image, however, the optical quality is insufficient due to a large amount of aberration fluctuations occurring during close-up photography compared to when focusing on an object at infinity. Accordingly, in order to maintain a favorable optical quality for a photographing distance ranging from infinity through to a close-up distance, a macro lens system has been proposed that employs a so-called “floating method”, in which focusing is performed by moving a plurality of lens groups by differing amounts to suppress aberration fluctuations that occur during close-up photography.
Patent Literature Nos. 1 through 4 each disclose a macro lens system which employs a floating method. In order to achieve a lens system that employs a floating method in a photographing apparatus, in which a further miniaturized image sensor is installed, in theory it is only necessary to scale down each numerical embodiment of the macro lens systems of Patent Literature Nos. 1 through 4. However, when such a scaled-down model is adjusted to lens element thicknesses and distances between lens elements that are determined with consideration of workability and assemblability, the balance of aberration corrections is lost, so that various aberrations increase and the optical quality becomes insufficient.
In each macro lens system of Patent Literature Nos. 1 through 4, an aperture diaphragm is included within a focusing lens group, which moves during focusing. Therefore, when the macro lens system of each of Patent Literature Nos. 1 through 4 is applied to an interchangeable lens, in which a shutter unit is mounted within the lens body, that is typified by a non-reflex camera (mirrorless camera), the shutter unit must be moved with the lens body during focusing, unavoidably complicating and enlarging the floating mechanism. Furthermore, since motors or actuators are required to cater to the number and weight of the focusing lens group(s), the lens system that includes a lens barrel increases in size.